Banning LCP, Ramakers IHGB, Rosenberg PB, et al. - In the present study, the researchers sought to explore trajectories of depression and apathy over a 5‐year follow‐up period in (prodromal) Alzheimer Disease (AD) and to relate these trajectories to AD biomarkers. Utilizing growth mixture models for two cohorts (NACC, n = 22 760 and ADNI, n = 1,733), the trajectories of depression and apathy (measured with the Neuropsychiatric Inventory or its questionnaire) were separately modelled. Utilizing bias‐corrected multinomial logistic regression, the trajectories in ADNI were associated with baseline CSF AD biomarkers (Aβ₄₂, t‐tau, and p‐tau). Multiple classes have been identified, with no symptoms in the largest classes over time. Lower Aβ₄₂ and higher tau (ie, more AD pathology) were correlated with an increased probability of depression and apathy over time relative to classes without symptoms. Lower Aβ₄₂ (but not tau) was correlated with a steep increase of apathy, while higher tau (but not Aβ₄₂) was related to a steep decrease of apathy. AD biomarkers are correlated with the depression and apathy trajectories of individuals on the AD spectrum.